Below is a simple fix for blackberry bold white screen problem. I tried it and managed to resurrect several blackberry bold 9780 phones. Let me know if it works for you.
1) Turn on the phone and wait for several minutes until it fully boots up.
2) Press the lock button + button P + lower right corner of the screen simultaneously.
3) It may require to do #2 several times in order for it to work.
The reason being is that the LCD connector may be loose. The connector/cable is directly beneath the p key. By pressing the key and lower
right corner of the screen, it helps to align them. Pressing the unlock button is just to reset/turn on the screen to see if it fixes the white screen.
Good luck and leave a comment whether this works for you!